Evaluation method for heart failure using RR sequence normalized histogram

Histogram and scatter plot are important graphical indices for heart rate variability (HRV) analysis. However, they are difficult to quantify the complexity for time series and have little specificity to some cardiovascular diseases. This paper proposed a new graphical method for HRV analysis, which was named as RR sequence normalized histogram. Based on the analysis of RR sequence normalized histogram, three quantitative indices were defined: center-edge ratio (CER), cumulative energy (CE) and range information entropy (RIEn). To verify the validity of the new method, a total of 120 subjects (60 heart failure subjects and 60 healthy control subjects) were enrolled and the three indices were calculated respectively. A Wilcoxon rank sum test showed that: CER (p = 0.232) and CE (p = 0.417) had no statistical differences between heart failure and healthy control group while RIEn (p = 0.027) had. This indicated that the new method had a potential application in evaluating the heart failure and the index RIEn had a better effectiveness than the other two indices.